Apparatus currently exist for moving an object in a defined plane. These apparatus utilize manual or motorized systems to move the object in one defined direction within the plane, for example, the x direction, and use a second manual or motorized system to move the object in a direction within the plane that is perpendicular to the first, for example, in the y direction. The use of the exemplary “x direction” and “y direction” terms, of course describes movement in an XY plane. It should be appreciated that such terms can be used to define any plane, inasmuch as a plane is a two-dimensional surface, with one dimension being denoted as “x” and the other being denoted as “y”. Such terms are employed in the present disclosure.
The aforementioned apparatus is referred to as an “XY translation stage,” and many configurations are known to those familiar in the art. Typical suppliers include Franklin Mechanical and Control Inc. (Gilroy, Calif., USA) and Physik Instrumente L.P. (Auburn, Mass., USA, also known by PI L.P.). From a review of the translation stages provided by these entities as well as those specifically in U.S. Pat. No. 5,142,791 (Hitachi, Ltd., Tokyo, Japan), U.S. Pat. No. 5,408,750 (Mitutoyo Corporation, Tokyo, Japan), and U.S. Pat. No. 6,809,306 (Olympus Optical Co. Ltd., Tokyo, Japan), it can be seen that the means for managing the movement and tolerances of the movement are varied. It can also be seen that the movement may be manual, or motorized, including but not limited to servo, stepper and piezoelectric motor movement.
An example of the prior art is provided in FIGS. 1A, 1B and 1C, which illustrate a typical XY translation stage. In FIG. 1A an X stage 1 is shown to move a platform 7 in the X plane. A primary drive mechanism 6, which may be either manual or motorized, is connected to a lead screw 3 by a connector 5. The lead screw 3 is bearing mounted to mounting brackets 2a and 2b, which are generally affixed to a stationary surface. A guide rod 4 is also mounted to the mounting brackets 2a and 2b, and the platform 7 includes a through bore 8 through which the guide rod 4 extends so that the platform 7 can move along the guide rod 4. The platform 7 also either includes a threaded bore 9 or is equipped with a ball nut so that, as the lead screw 3 is rotated by the primary drive mechanism 6, the platform 7 is moved through the plane in the X direction. Guide rod 4 prevents rotation of platform 7.
In FIG. 1B a Y stage 10 is shown to move platform 16 in the Y plane. A primary drive mechanism 15, which may be either manual or motorized, is connected to a lead screw 12 by connector 14. The lead screw 12 is bearing mounted to mounting brackets 11a and 11b, which as will be described more fully below with respect to FIG. 1C are affixed to the platform 7. A guide rod 13 is also mounted to the mounting brackets 11a and 11b, and the platform 16 includes a through bore 18 through which the guide rod 13 extends so that the platform 16 can move along the guide rod 13. The platform 16 also either includes a threaded bore 19 or is equipped with a ball nut so that, as the lead screw 12 is rotated by the primary drive mechanism 15, the platform 16 is moved through the plane in the Y direction. Guide rod 13 prevents rotation of platform 16.
In FIG. 1C the platform 16 of Y stage 10 is affixed to the platform 7 of X stage 1 by affixing mounting brackets 11a and 11b to the platform 7. The combined stages in FIG. 1C represent a typical XY translation stage 17 where the object to be moved is placed upon platform 16 and, thus mounted, can be freely moved in the Y direction through rotation of the lead screw 12 and in the X direction through rotation of the lead screw 3. Hence, platform 16 and the object thereupon are capable of being moved freely in the X and Y directions being constrained only by the length of the respective lead screws 3 and 12.
In the current art as shown in FIG. 1C (and in known variations thereof), it can be seen that the degree of movement is constrained by the pitch of the lead screws 3 and 12 and rotational control of the primary drive mechanisms 6 and 15. For example, given a lead screw 3 with a pitch of 5 threads per millimeter and a stepper motor capable of stepping at 1 degree of rotation per step driving the lead screw 3, each step of the stepper motor will move the platform approximately 0.56 micrometers. Thus, the degree of incremental movement may be changed by the selection of the drive and lead screw.
As known, such translation stages are often employed for scanning an object. As used herein, “scanning” is to be understood broadly to refer to defining or analyzing a desired surface area of an object, whether by probe, stylus or electromagnetic beam (e.g., visible light, electron beam, laser, etc). For example, these translation stages are often employed in scanning probe microscopy, scanning beam microscopy, and optical inspection devices and the like. With the aforementioned XY translation stages, in order to scan an entire defined XY plane, the direction of travel must be stopped and reversed when the platform has reach the limit of travel defined by the length of the lead screw. Hence, movement is stopped and direction changed many times during a scan. With the components given in this example, movement would have to be stopped and direction changed approximately 180,000 times to scan a 100×100 mm plane, and the starting, stopping, speed and direction of translational movement must be controlled either by manual operator intervention or by a method of computer motor control of two primary drive mechanisms, one for the X stage and one for the Y stage.
Though the art is populated with various translation stages, there exists room for improvement thereon by providing apparatus for more easily automated translational movement. The present invention is designed to reduce both the motion management and XY translation stage complexity.